It was discovered that Dovecot incorrectly handled client certificates. A remote attacker in possession of a valid certificate with an empty username field could possibly use this issue to impersonate other users. References: https://security-tracker.debian.org/tracker/source-package/dovecot https://usn.ubuntu.com/usn/usn-3881-1 https://usn.ubuntu.com/usn/usn-3881-2
Created dovecot tracking bugs for this issue: Affects: fedora-all [bug 1673416]
External References: https://www.dovecot.org/list/dovecot/2019-February/114575.html
This basically affects installation which enable client-side certs. When authenticating with a cert which has empty "user" field, vulnerable versions take the loginame from the user. If no additional password is configured this will allow the user to impersonate anyone else in the system.
Mitigation: Attack can be migitated by having the certificates with proper Extended Key Usage, such as 'TLS Web Server' and 'TLS Web Server Client'. Also client-side certification authentication can be turned off using: auth_ssl_require_client_cert = no auth_ssl_username_from_cert = no
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2019:3467 https://access.redhat.com/errata/RHSA-2019:3467
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2019-3814
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2020:1062 https://access.redhat.com/errata/RHSA-2020:1062